Reinforced sheet material



July 11, 19 7 J. w. SANDERSON REINFORCED SI'IEE'I MATERIAL 2 Sheets-Shget 1 Filed Dec. 31, 1963 JOHN w. SANDERSON ATTOR EY;

July 11, 196 J. w. SANDERSON REINFORCED SHEET MATERIAL 2 Sheets-Sheet Filed Dec. 51 1963 INVENTOR JOHN W. SANDERSON BY 5 i M ATTORNEYS United States Patent C) 3,330,330 REINFORCED SHEET MATERIAL John W. Sanderson, Chicago, 111., assignor to Signode Corporation, a corporation of Delaware Filed Dec. 31, 1963, Ser. No. 334,832 1 Claim. (Cl. 160327) The present invention relates to reinforced plastic sheet material, especially stock material which can be made available in any desired length in roll form, and which is adapted to resist applied forces in a new, different and valuable manner.

More particularly, plastic sheet material, especially thin sheets thereof, possess only limited capacity to resist applied forces, and this is especially true when the applied force is concentrated upon a limited area of the sheet. The invention relates to reinforced plastic sheet material including a plurality of longitudinally disposed tensile elements or ligatures adapted to resist tensile loading without transmitting this load to the sheet material. At the same time, and as a result of the novel construction of the invention, moderate forces applied over large areas of the sheet material and which forces possess lateral force components, are instantly and uniformly transmitted to the sheet material in a manner which avoids the concentration of forces and the failure attendant thereupon. Moreover, the invention permits longitudinal adjustment of and independent longitudinal tensioning of the sheet material without disturbing the longitudinal tensile elements to provide a new capacity for the disposition of sheet material over the space defined between spacedapart frame elements of a structure. Still further, the invention preferably contemplate a construction in which the longitudinal tensile elements are spaced from the lateral margins of the sheet material to provide a product in which the lateral margins are unstressed and possess superior resistance to tearing.

It should be noted that plastic heet material is frequently used to obstruct an opening between spaced apart frame elements, but conventional materials are subject to serious inadequacies. For example, when plastic sheets are used to cover large openings in a partly completed building in order to keep out wind while letting in sunlight, the plastic heet is not adapted to resist the force of a human being. Workmen have fallen out of such partly completed buildings as a result of a momentary inattention, not infrequently causing serious injury and death. The presence of the plastic sheet may give the illusion of a wall, but this wall cannot support any heavy load. Aside from the obvious danger noted above, conventional plastic sheet material when used as a wall is agitated by the wind, and the forces so imposed concentrate at points causing the sheet to rip. This is wasteful and, of course, it greatly impairs the capacity of the sheet material to perform its intended function of keeping out the wind. Conventional reinforcement of plastic sheet material used a a wall is of little help, since it merely provides barriers against which the wind-agitated sheet bears to concentrate the applied forces. At the same time, the individual reinforcements cannot be individually tensioned since there has not previously been any feasible way of tensioning several elements without causing extensive wrinkling which is unsightly and conducive to stress concentration or Without preventing the stress imposed upon the reinforcing elements from being destructively transmitted to the sheet material. Still another problem is the provision of controlled ventilation since, if small holes are cut to let a small amount of air through the sheet, these small holes weaken the sheet, since tearing forces automatically concentrate at these sites.

In accordance with the present invention, there is provided a composite plastic sheet material having sealed therein a plurality of longitudinally extending ligature elements disposed parallel to one another. These ligature elements are free for longitudinal sliding movement within the composite, but the composite is sealed immediately adjacent both sides of the ligature to prevent any significant lateral movement of the ligatures within the composite. In this Way, the ligatures are relatively snugly fitted within generally parallel sleeves formed in the composite so that lateral forces applied to the composite are immediately transmitted to the ligatures while longitudinal forces imposed upon the ligatures are not significantly transmitted to the composite.

It is preferred to employ at least one intermediate ligature in addition to at least one ligature adjacent each of the lateral margins of the composite. Also, and to avoid the concentration of forces, these ligatures should be in parallel and should not intersect. Still further, and to avoid the imposition of force upon the lateral edges of the composite and thereby provide superior resistance to tearing forces at these edges, the marginal ligatures are preferably spaced inwardly from the lateral edges to provide lateral edges which are loose and free.

Preferred practice of the invention involves the disposition of a plurality of parallel ligature elements, preferably straps and most especially nylon, polypropylene, rayon or other plastic or other non-metallic extendible strapping material with or without fiber or other reinforcement incorporated therein, between a pair of relatively thin plastic sheets which are then strongly secured to one another at least in the longitudinal areas adjacent each of the straps and preferably substantially completely throughout their contacting surfaces, but the inner faces of the sheets are not significantly sealed to the straps.

The result is a reinforced plastic sheet, but one which is quite different from the conventional plastic sheet because the strap elements may be tensioned without tensioning the sheet-material as a whole; this sheet material being capable of relative movement with respect to the longitudinal axes of the straps so that any tensions or any variation of tension which may occur on any strap or any series of straps, is not carried over into the sheet material thereby avoiding the imposition of localized stress on the sheet material and permitting plastic sheets which are thin, light, and relatively lacking in strength to withstand considerable loading and permitting diverse utility in tents, boat covers, building enclosures, green houses, grain doors, open top vehicle conveyances such as railroad gondolas and hopper cars, trucks, trailers, barges, airplanes, etc.

As a feature of the present invention the sheet material discussed hereinbefore is extended across spaced members such as a frame and the straps are secured to fastener elements which will be discussed more fully hereinafter but which have the capacity of grasping the strap while permitting the strap to be tensioned. At the same time, the outer portions of the fastener elements are formed of hook shape to surround the frame elements and the sheet material is extended between the hook of the fastener and the frame. As a result, and after the straps have been tensioned, the sheet material, which is free to move longitudinally of the straps, can be separately tensioned with the tension applied to the hooks by the strap being relied upon to frictionally hold the sheet material in place against the frame element.

The invention includes, as a subsidiary feature thereof, the provision of composite stock material which is easily modified as desired to include ventilation Openings permitting controlled passage of limited quantities of air through the composite sheet material. This is achieved by non-adhesively incorporating insert pieces within the composite so that the inner faces of the plastic sheets are not secured to the insert. The final product can then be cut to reveal the insert which, when it is partly or fully removed, permits non-aligned openings to be made in the plastic sheets enabling air to drift through the composite at a'rate which is controllable by varying the size, shape and position of the openings or by the partial presence of some bafile element positioned within the composite. When air passes slowly through the composite, tearing forces are greatly reduced.

The invention will be more fully described in connection with the accompanying drawings in which:

FIG. 1 is a perspective view showing a preferred con struction in accordance with the invention, with the forward portion of the upper plastic sheet turned back to facilitate understanding;

FIG. 2 is a cross-section taken on the line 2-2 of FIG. land presented on a greatly enlarged scale;

FIG. 3 is a perspective view similar to FIG. 1 and showing the use of transverse ligature elements;

FIG. 4 is a perspective view similar to FIG. 1 and showing the use of a strap gusset to reinforce the sheet material in the vicinity of the strap; 7

FIG. 5 is a cross-section taken on the line 55 of FIG. 4 and presented on a greatly enlarged scale;

FIG. 6 is a fragmentary perspective view, partially in section and showing a construction used for venting;

FIG. 7 is a partial perspective view showing the space between frame elements closed in accordance with the invention; and

FIG. 8 is a cross-section taken On the line 7-7 of FIG. 7.

Referring more particularly to FIG. 1, there is shown a portion of a length of composite stock material 10 constructed in accordance with the present invention. This stock material is composed. of upper and lower plastic sheets 11 and 12, between which is sandwiched a plurality of longitudinally extending ligature elements arranged in spaced-apart parallel relation, these ligatures being shown in their preferred form, e.g., straps. The longitudinal straps include marginal straps 13 and intermediate straps 14 (only one of which is shown).

The inner contacting surfaces of the plastic sheets 11 and 12 are securely sealed together by means of adhesive, or by application of heat as hereinafter set forth. On the other hand, the plastic sheets are not sealed to the straps.

This specific structure will be more fully apparent in FIG. 2 in which numeral 15 identifies a secure seal and numeral 16 identifies a lack of securement.

It should be observed that strap 14 is snugly fitted within a sleeve formed between the unsecured portions of sheets 11 and 12, this sleeve being identified by numeral 17. In view of the snug fit, no significant lateral movement of the strap is possible and lateral forces imposed upon the secured together sheets 11 and 12 are immediately transmitted to the strap. Also, and because the strap 14 is unsecured or only insignificantly adhered to theinner surfaces of sheets 11 and 12, these sheets and the strap are adapted for longitudinal displacement with respect to one another. Accordingly, if the strap is moved longitudinally when it is tensioned to secure the composite stock material 10, this movement is not transmitted to the secured together sheets 11 and 12. Correspondingly, when lateral forces are imposed upon the secured. together sheets 11 and 12, these forces cannot concentrate at any point because such concentration would tend to longitudinally displace the secured sheets with respect to the strap, and the fact that such displacement can occur securely bonded together, but these sheets will not bend to the straps interposed therebetween.

In view of the simplicity and effectiveness of heat sealing for the production of stock material in accordance with the invention, the utilization of thermoplastic sheet material is particularly preferred. Examples of preferred thermoplastic sheet material in accordance with the invention are polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, etc. This thermoplastic sheet material may be transparent, translucent or opaque, it may be decorated if desired and embossed either before, during or after heat sealing in accordance with the invention. Also, the sheets which are superposed may be of the same type or thickness or of different type or thickness. Care should be taken to insure that the manner of securing the thermoplastic sheets to one another does not also adhere the sheets to the strapping. When heat scaling is used, the temperature, pressure, etc., must be selected in accordance with the materials chosen to constitute the sheets and the strapping so that a secure heat seal is effected between the sheets and the strapping is unaffected.

The ligature elements, preferably straps, which are used polypropylene and nylon strapping being particularly preferred. The choice of resilient strapping is of especial significance because it is intended that these straps be independently and strongly tensioned by hand or by mechanical manipulation. On the other hand, relatively non-resilient strapping such as metal straps can be used, especially when the strap-confining sleeves are reinforced, as will be discussed hereinafter.

It will be understood that the composite materials which are produced in accordance with the present inven-. tion may be quite large in size, e.g., these might have a width of approximately 8 feet for use in the enclosure of partially completed buildings. In such large structures, it will be understood that many straps will be employed, and not merely three, as has been illustrated in FIG. 1. The number of straps which is used will depend upon the strength requirements of the completed product so that the reinforcing straps in accordance with the invention may be closely spaced in certain instances where great strength is required, as in the construction of webbing for use in furniture, or these straps may be widely spaced where load bearing capacity is of secondary consideration, e.g., in protective coverings such as boat cove-rs, or in the construction of partitions as in a childs play pen.

While the present invention particularly contemplates stock material in which the ligature elements extend longitudinally, transverse ligature elements for added strength are also contemplated, especially when the transverse ligatures are longer than the width of the sheet material with which they are used so as to extend beyond the lateral margins of the sheet to be immediately available for tieing purposes. This is of particular significance in furniture and in awningsintended to bear the weight of and longitudinal straps toward a heat or other sealing device (not shown), the lateral straps 18 being placed in position in predetermined spaced-apart relation as the sheets advance. As discussed in connection with FIGS. 1 and 2, the sheets 11 and 12 are adhered in face to face contact but not to either straps 13, 14 or 18 and the straps 18 are not adhered to either straps 13 or 14. In consequence, the straps 13, 14 and 18 are capable of individual movement along their respective longitudinal axes.

As will be evident, it is economically desirable to employ the thinnest possible plastic sheet material. In some instances and with very thin plastic sheet material there is some tendency for the sheets to rip against the edge of the strap. This tendency can be reduced with minimum material consumption by wrapping the strapping with thermoplastic heat-scalable material so that there will be an increased thickness of plastic material in the immediate vicinity of the straps to better resist tearing forces. This expedient is shown for one of the marginal straps in FIG. 4 in which gusset 19 is simply folded about the advancing strap. In the final product, the sheets 11 and 12 are secured to one another and to the gusset 19 and the interior surfaces of the gusset 19 are sealed to one another, but not to the strap enclosed within the same.

The sealing of the outer sheets 11 and 12 to the gusset 19 and the sealing of the interior surfaces of the gusset 19 to themselves to provide a sleeve within which the strap 13 can move longitudinally is more clearly shown in the cross-section of FIG. 5. The interior surfaces 36 and 37 of gusset 19 are sealed together by heat or other adherent means as is shown by numeral 38. On the other hand, the gusset 19 is not sealed to the plastic strap 13, numeral 39 identifying the lack of securement, thereby providing a sleeve in which strap 13 can move longitudinally. The interior surfaces of sheets 11 and 12 are sealed to the exterior surfaces of the gusset to form the composite of the invention.

Various materials may be inserted between the superposed plastic sheets for diverse purposes. Thus, fiber or continuous filaments may be blown, or thrown, or dusted upon the lower sheet for reinforcement or decoration. Pieces or sections of material such as a sheet of printed paper may be incorporated for decoration, instruction, advertising or identification. Of particular significance is the use of inserts which are nonadherent and which may be partially or fully removed from between the secured together sheets. Such a construction can serve many purposes, but it is especially useful in connection with the provision of ventilating openings for controlled air fiow through the composite stock material.

The construction of a ventilation port is shown in FIG. 6. Assuming that one had interposed a fiber disc 20 between the superposed plastic sheets 11 and 12 in the construction shown in FIG. 1, then this disc would be nonadherently entrapped between the secured together sheets. If one then cuts, stamps or otherwise severs sheet 11 in a semicircle through to the disc, the cut being identified by numeral 21, then one can partially or fully withdraw disc 20 from its pocket 22 between the secured sheets. FIG. 6 shows disc 20 in a partially withdrawn position. Cutting a smaller opening 23 in lower sheet 12, one has a ventilation opening in which air can pass through the composite 10 as shown by arrows 24 and 25, and the amount of air can be controlled by the position of disc 20.

The same concept of cutting through one or both of sheets 11 and 12 to expose a nonadherent piece entrapped between the sheets can be used for diverse purposes, including the formation of window areas within a composite in which one or both of sheets 11 and 12 are opaque.

The stock material of the present invention is of particular importance in closing the space between frame members, it being understood that the term frame members is used in its broadest connotation to embrace spacedapart structure of any material and cross-section.

In this utility, the straps are used as tie members and the secured-together sheets close the space. It will be immediately apparent that the invention requires that the tensile loading be placed upon the straps, that the securedtogether sheets extend around the frame elements to completely close the space, and the secured-together sheets be adjustable independent of the straps. This is accomplished without waste of sheet material, using the construction shown in FIGS. 7 and 8.

Referring more particularly to FIGS. 7 and 8, numeral 26 identifies spaced-apart frame members held in that position by end members, one being indicated by numeral 27 as shown. The frame members are illustrated as tubular as a matter of convenience, but it is to be understood that these members may have any other form or shape without departing from the scope of the invention. The composite stock material 10 is extended across the space and around the frame members 26, the portion extending around the frames being identified by numeral 28. The portions of upper sheet 11 overlying the strap are cut or stripped away adjacent each end of the strap to expose the strap and permit the handling thereof. The strap is then guided through a structure equipped at one end thereof to maintain the strap under tension and formed, at the other end thereof, with a frame-grasping hook. The strap tension-maintaining means is broadly identified by numeral 29 and the hook, which is shaped to correspond with the cross-section of the frame element, is identified by numeral 30.

It will be noted that the book 30 not only grasps the frame member, but it also clamps portion 28 against the frame elements. As a result, the opposite ends of the straps can be threaded through strap-maintaining means 29 and drawn tight and this will function, via hooks 30, to clamp the composite material 10 in place. However, each strap is separately tensioned and the sheet 10 will be badly wrinkled, but this is uniquely accommodated in the invention by virtue of the fact that the sheet 10 is longitudinally displaceable with respect to the straps. Indeed, it is merely necessary to pull strongly on portions 28 to force the sheet 10 to move against the friction imposed by hook 30 to thereby adjust the position of sheet 10 and thereby remove the wrinkles. The result is far more than the elimination of an unsightly condition, for these wn'nkles, if not removed, concentrate forces and lead to tearing when strong winds are encountered, as indicated hereinbefore.

FIG. 8 shows the details of a securing device which may be used and the manner in which the strap ends are withdrawn from the stock material for engagement by the strap tension-maintaining means 29. Thus, sheet 11 of the strap-confining sleeve formed by sheets 11 and 12, is cut or broken apart as by a stripping action, as indicated at 31, to free strap end 32 which is threaded through a self-locking buckle in which the buckle elements 33 and 34 are integral with the body of the fastener and element 34 is flexible as a result of notch 35. The threading is effected as shown in the drawing, and tension is applied as indicated by arrow B.

The invention is defined in the claim which follows.

I claim:

In combination, spaced-apart frame elements defining a space therebetween and reinforced plastic sheet material extending longitudinally across said space and around said frame elements to close said space, said sheet material comprising a pair of superposed plastic sheets having sandwiched therebetween a plurality of spaced-apart, parallel, longitudinally disposed ligature elements, said superposed plastic sheets being securely sealed to one another at the contacting surfaces thereof to form sleeves embracing said ligature elements, said ligature elements being snugly fitted within said sleeves and substantially unsecured to said sleeves whereby said ligature elements are free to move longitudinally within said sleeves while lateral movement of said ligature elements with respect to said superposed plastic sheets is effectively precluded, the portions of one of said plastic sheets overlying the terminal portions of said ligature elements being cut to expose the terminal positions of said ligature elements, fastening elements associated with said frame elements and each comprising an inner tension-maintaining means for said ligature elements and an outer frame-grasping hook, said terminal portions of said ligature elements being operatively engaged with and maintained under tension by the tension-maintaining means of said fastening elements to tension said ligature elements and bias the hook of said fastening elements against said frame elements, and the hook of said fastening elements frictionally clamping the portions of said superposed sheets which extend around said frame elements against said frame elements whereby said superposed sheets and said ligature elements may be separately tensioned.

References Cited UNITED STATES PATENTS Stein 161112 X Ladon' 161-71 Geerlings 161140 X Strauss 16195 X Moon 161143 X Robins.

Biefeld 161-93 X Holt 156-304 X Russell 161142 X Weitzel 161101 Trope 161112 15 ALEXANDER WYMAN, Primary Examiner.

W. A. POWELL, Assistant Examiner. 

